1. Field of the Invention
This invention relates to brake testing systems and more particularly, to an system for measuring brake shoe forces applied in the brake system of a railcar.
2. Description of the Prior Art
A railcar typically is equipped with a air brake system for operating brake shoe assemblies that apply brake forces to the wheels. The pressurized brake system is supplemented by a hand brake arrangement for applying a manual braking force. In order to maintain consistent and proper functioning of the railcar braking system, it is necessary to test such parameters as brake shoe forces and hand brake force during assembly or conversion of a railcar. Present requirements establishing minimum permissible brake force levels attempt to insure proper braking during operation of the railcar. The American Association of Railroads (AAR) have required that dynamometers for testing brake shoe systems meet specific standards for accuracy. Several static measuring systems have been developed in the past to quantitatively measure the forces exerted by the brake shoes and hand brake.
Existing brake testers employ several techniques of force measurement that suffer from a variety of shortcomings. For example, many brake testing devices are relatively inaccurate, bulky, and incapable of being easily transported from place to place as is advantageous in use. Other brake force testers do not permit the convenient simultaneous measurement of multiple brake shoes, hand brake force, and cylinder pressure. One technique of testing brakes employs force transducers, having strain gauges and the like, that are affixed to selected brake components of a railcar for making measurements. Some of the testing devices simulate brake shoes or other components so that a reading of force is attainable. Prior designs of brake shoe transducers are relatively expensive to fabricate and do not attain optimim results in use. It is therefore desirable to provide an easily transportable brake force tester attaining concurrent measurement of multiple brake forces with enhanced accuracy.